The invention relates to a two shot molding method which can be used to make a fastener device having a fastener portion and integral seal portion of different material. More particularly, the invention relates to a fastener device comprising a fastener part having a plastic head and anchor stem with prongs and a flexible seal of different material integral with the fastener part and the two molded together in a two-shot molding technique.
More parts of vehicles, particularly trim parts, are being formed of molded plastic which trim parts are secured to portions of the vehicle body through fastener devices. A typical trim pad mounting fastener is that shown in U.S. Pat. No. 3,249,973 of Seckerson wherein there is provided a fastener with a stud formed from a moldable material so as to have a head and a snap-engaging stem or prong extending therefrom. The head has a substantially circular sealing flange adjacent the stem and a retaining flange spaced along the length of the head from the main flange. The stem has means such as being shouldered and slotted, whereby the stem may be flexed when inserted into an aperture and return to its normal configuration to secure the fastener in the aperture. The sealing flange is in the form of a skirt which is dished and concave towards the stem thereby exhibiting a certain degree of resiliency. When the fastener is properly located in securing a trim pad, the skirt is flattened against the outer surface of the panel to form a seal around the aperture.
However, one of the problems of the type of fastener exemplified by Seckerson is that the sealing flange which is in the shape of a skirt, is molded of the same material as the other parts of the head and the stem.
Often the material used for fabricating strength and rigidity into the retaining flange and the stem is not the most advantageous for producing a sealing flange for the purposes of sealing an aperture and thus the sealing flange fails in its objective to act as an effective seal even when there is some resiliency about its periphery.
Attempts have been made to formulate seals of separate material, the seal material being more effective as a seal, but this requires a step of connecting the seal with the fastener prior to use. If this is done in the shop, there is a problem with the seals becoming separated from the fastener stem during shipping and handling. In the alternative, it is too labour intensive to connect the seals with the fastener just before installation. Indeed with today""s modern assembly techniques, it is difficult to visually check on whether each fastener has a seal on it before it is used.
Accordingly, it would be advantageous to provide a fastener device adapted for securing molded trim which has a seal integral with the head and stem but of a material which enhances the sealing capabilities of the seal portion and is not of the same material as the other more rigid parts of the head and of the stem. Further, it would be advantageous to have a fastener device wherein its securing aspects and its sealing capabilities are each provided with materials which enhance their respective functional purposes.
Still further, it will be advantageous to be able to mold a device, the fastener device only being one exemplary device possible, having parts of different material wherein the molding takes place in at least a two step process wherein a portion of the device is molded first and the second or subsequent parts are molded in the same mold, using the molded first part as, a conduit of material or to define part of the shape or configuration of the second part.
The invention in one broad aspect pertains to a method of fabricating a device having at least two parts molded of different materials, comprising providing a mold cavity having at least three cavities, a first cavity defining a configuration of a first part of the device, a second cavity defining a configuration of a second part of the device and a third cavity defining a configuration of a third part of the device, the cavities initially being in flow communication with each other with flow communication between the first and third cavities being through the second cavity. The first and third cavities are temporarily closed off from the second cavity including closing flow communication between the first and third cavities. A first material is injected into the second cavity to mold the second part of the device and then flow communication between the first and third cavities is opened. A second material is injected into the first and third cavities, the second material flowing between the first and third cavities through at least one portion of the second part of the device as molded wherein the at least one portion of the second part effectively defines a passageway for the flow of second material between the first and second cavities to form the first and third parts of the device. The device is from the mold cavity whereby the device as molded has parts of different materials molded sequentially together.
More particularly, the invention comprehends molding a fastener device comprising a molded rigid fastener part and a molded seal part, the rigid fastener part having a head, a fastening element for fastening association with an aperture and a neck intermediate the head and the fastening element. The seal part has a collar portion surrounding the neck and a flexible skirt portion extending radially outwardly from the collar portion. The seal part is of a material different from the material of the rigid fastener part and the neck is formed within and is substantially covered by the collar.
Preferably, the method is used to fabricate a fastener device wherein the fastener device comprises a head portion, a neck portion and a fastening element, and a seal portion, the seal portion being molded of the first material in the second cavity and the head portion and the fastening element being molded of the second material in the first and third cavities, the neck portion being formed of the second material within and defined by a collar part of the seal portion.
The invention also pertains to a fastener device and method of manufacture, the device having a rigid fastener part and a seal part attached thereto, the seal being preferably of a different material to that of the clip. The fastener part has a head portion integrally connected with a prong or stem portion through a neck. In a two shot molding technique, the seal part is molded first and the rigid fastener part is molded subsequently in such fashion that the seal part is properly located and permanently connected to the rigid part of the fastener device. Preferably the seal is molded with a cylindrical collar and the fastening element is molded by injecting material to form the prong or stem through the collar. The collar surrounds the neck of the fastening element in the final form of the fastener.
Although the fabrication method has been particularized herein with respect to making a fastener device, it will be appreciated that the molding technique can be used to fabricate other devices which have parts of different material wherein part of the device is molded first and the other part or parts of the device are molded using at least a portion of the already molded first part as a conduit or passageway in molding portions of the second part. In other words, the first part effectively defines at least a portion of the mold cavity of the second part.
Other aspects of the invention will become evident from a review of the preferred embodiments of the invention setforth hereinafter.